Lighting devices, such as incandescent light bulbs and light emitting diodes LED lamps are available in various designs. Some lighting device designs are compatible with existing lighting fixtures and sockets. For example, a lighting device may be provided with a threaded base which may be screwed into a socket, i.e. an Edison screw fitting. Such a lighting device comprising a threaded base needs to be hand-tightly fixed to the socket to ensure electrical connection to the socket such that the light source of the lighting device may be powered.
The lighting devices that are currently available on the market are predominantly rotational symmetric. The light emission and visual appearance of such a lighting device does not significantly depend on the rotational angle of the lighting device after it is screwed into the socket of a luminaire. In other words, the actual rotational position of the lighting device, after it is hand-tightly fixed to the socket, does therefore not influence the visual appearance of the luminaire. This same reasoning holds for a lighting device having a rotational symmetric light emission, since the directionality of the light emitted from the luminaire is not affected by the rotational position of the light source.
If, however, the lighting device and/or its light emission is rotationally asymmetric the visual appearance and/or directionality of the light emission depend on the rotational angle of the lighting device.
A lighting device provided with a threaded base is typically screwed into a socket until it makes electrical contact and is hand-tight. However, the appearance of a lighting device being rotationally asymmetric or the light emission of a lighting device having a rotationally asymmetric light emission may be pointed at a non-ideal angle when screwed into the socket.
Hence, it is desirable to be able to rotationally adjust the position of the lighting device or to direct its light emission by turning the lighting device.
It may be possible to turn the lighting device somewhat to aim it correctly but that will loosen the device in the socket and may diminish or even break the electrical connection. This condition could either cause the light to go out, or result in a poor electrical connection that gets hot and creates a fire hazard.
In U.S. Pat. No. 8,147,267 a solution to this problem is presented. According to U.S. Pat. No. 8,147,267 a spring coil biased movable conductor mounted in the center of the base is used in order to solve the problem of being able to turn a rotationally asymmetric lighting device with retained good electrical connection between the lighting device and the socket.
However, there is a need to find new means to direct asymmetric lighting devices with a screw-in type base.